Fix link to SQLAlchemy Hybrid Attributes docs
Fix link to SQLAlchemy Hybrid Attributes docs

Broken link: http://docs.sqlalchemy.org/en/improve_toc/orm/extensions/hybrid.html
New link: https://docs.sqlalchemy.org/en/14/orm/extensions/hybrid.html
coleifer/peewee,coleifer/peewee,coleifer/peewee